Per- and polyfluorinated alkyl substances (PFAS) are a group of anthropogenic compounds which due to their unique properties are used in various domestic and industrial applications. However, those properties make PFAS extremely difficult to break down resulting in serious contamination of the environment. In Sweden, a major issue is the PFAS-contaminated soil near military training areas and airports. The excess use of firefighting foam containing PFAS affects nearby areas significantly, as PFAS can leach out of soil and contaminate water sources. In order to overcome this problem, sorption techniques may be used which can stabilize PFAS. A potential sorbent is biochar, a carbon material produced by pyrolysis of organic biomass. This study aimed to investigate the efficiency of sorption methods using biochar as a potential remediation technique. Soil samples from a regional rescue service area (Räddningstjänsten Östra Götaland; RTÖG) were collected. The soil had a total PFAS content of 76.8 ng/g dry matter (d.m.). The soil was subject to four different treatments: 1) untreated (control); 2) addition of mixture of 1% compost and 2.5 g/kg fertilizer (FC); 3) addition of FC and 2% w/w of sewage sludge-based biochar (BC-SS); 4) addition of FC and 2% w/w of activated biochar (BC-AC). A batch leaching test (ISO 21268-1:2019) was performed, and both the leachate and the residual fraction were analyzed for 36 PFAS with ultra-performance liquid chromatography coupled to tandem mass spectrometer (UPLC-MS/MS). The two selected extraction methods were solid phase extraction with weak anion exchange (SPE-WAX) for the leachate and a comprehensive method with acidic and alkaline digestion for the solid matrix. The results for the leachate fraction showed that the retention efficiency percentage obtained in the FC-treatment compared to the control was 15.2% of total PFAS. Meanwhile, in the sewage sludge-based and activated biochar treatments the retention efficiency percentages significantly increased to 94.8% and 99.5% of the total PFAS levels, respectively, compared to the control. In the residual fraction, the retention percentage for the control treatment relative to the initial soil was almost 48.1% and for the FC-treatment was 52.8%. Whereas, in the BC-SS and BC-AC the retention percentages were increased at 67.2% and 96.4% respectively. These values indicated that both types of biochar are effective in retaining the contaminants, with only a small contribution from the FC mixture. Of the two biochar types, the BC-AC was proven to be the most efficient sorbent, particularly with high retention of the longer chain PFAS and especially perfluorinated sulfonic acids (PFSAs). In conclusion, treatment with biochar, and especially activated biochar can prevent the PFAS from leaching into water and has a potential of immobilizing PFAS contaminants in the soil.